Adenosine Inhibition of 45Ca Uptake by Synaptosomes as Function of Time of Electrical Stimulation

Abstract

The effect of adenosine on ⁴⁵Ca uptake by rat brain synaptosomes electrically stimulated was studied as function of time of stimulation (10, 30, 120 s). Inhibition of ⁴⁵Ca uptake was more evident for 120 s.     

Edge-induced narrowing of dietary diversity in leaf-cutting ants

Much of the ecological alteration faced by human-modified Neotropical forests can be assigned to edge effects, including the proliferation of some voracious herbivores such as leaf-cutting ants. However, the underlying mechanisms/impacts of tropical forest edge on herbivores performance and their foraging behaviour (e.g. dietary diversity) have rarely been investigated. The goal of this study was, therefore, to determine whether and how the annual diet (i.e. species richness, diversity and the relative proportion of pioneer versus non-pioneer species of plant materials) of Atta cephalotes colonies differs in the forest edge versus the interior zone of a large remnant of Atlantic forest in northeastern Brazil. Among the key results was a strong habitat effect on dietary diversity (explaining ca. 40-50% of the variation), which, in edge colonies, decreased approximately by one fourth compared to interior colonies (inverse of Simpson's index: 3.7±0.84 versus 4.99±0.95). There was a predominance of leaf fragments collected from pioneer species in the diet in both habitat (86% in edge and 80.4% in interior). Edge colonies collected proportionally more fragments from pioneer species than colonies located in the forest interior. Our results are the first to demonstrate an edge-mediated relaxation of dietary restrictions in leaf-cutting ants. These findings render robust support to previous evidence indicating the reduction of bottom-up forces as a key factor explaining both edge-induced hyper-abundance and increased herbivory of leaf-cutting ants in human-modified Neotropical landscapes.     

Structures of the O-linked oligosaccharides of a complex glycoconjugate from Pseudallescheria boydii

Nonreducing O-linked oligosaccharides were obtained from the peptidorhamnomannan of mycelia of Pseudallescheria boydii by alkaline beta-elimination under reducing conditions. They were separated by gel filtration chromatography to give three oligosaccharide fractions. The major oligosaccharide from fraction 1 was characterized by a combination of techniques including electrospray ionization quadrupole time-of-flight tandem mass spectrometry (ESI MS/MS), matrix-assisted laser desorption ionization mass spectrometry (MALDI MS), nuclear magnetic resonance (NMR), and methylation gas-liquid chromatography-mass spectrometry (GC-MS) analysis. It was branched, with a principal chain of alpha-Rhap-(1 --> 3)-alpha-Rhap-(1 --> 3)-alpha-Manp-(1 --> 2)-Man-ol substituted at O-6 of mannitol with an alpha-Glcp-(1 --> 4)-beta-Galp group. Species containing one and two additional alpha-Glcp-(1 --> 4) substituents in the rhamnose branch were also present. The major component of fraction 2 was a substructure of oligosaccharide-1, lacking a hexose from the Glc-Gal branch. Fraction 3 contained a mixture of smaller, unbranched, oligosaccharides. In hapten inhibition tests, fractions 1 and 2 blocked the reaction between peptidorhamnomannan (PRM) and rabbit anti-P. boydii mycelium hyperimmune serum by approximately 75%, whereas fraction 3 inhibited by approximately 55%.     

8p22 MTUS1 Gene Product ATIP3 Is a Novel Anti-Mitotic Protein Underexpressed in Invasive Breast Carcinoma of Poor Prognosis

Background

Breast cancer is a heterogeneous disease that is not totally eradicated by current therapies. The classification of breast tumors into distinct molecular subtypes by gene profiling and immunodetection of surrogate markers has proven useful for tumor prognosis and prediction of effective targeted treatments. The challenge now is to identify molecular biomarkers that may be of functional relevance for personalized therapy of breast tumors with poor outcome that do not respond to available treatments. The Mitochondrial Tumor Suppressor (MTUS1) gene is an interesting candidate whose expression is reduced in colon, pancreas, ovary and oral cancers. The present study investigates the expression and functional effects of MTUS1 gene products in breast cancer.

Methods and Findings

By means of gene array analysis, real-time RT-PCR and immunohistochemistry, we show here that MTUS1/ATIP3 is significantly down-regulated in a series of 151 infiltrating breast cancer carcinomas as compared to normal breast tissue. Low levels of ATIP3 correlate with high grade of the tumor and the occurrence of distant metastasis. ATIP3 levels are also significantly reduced in triple negative (ER- PR- HER2-) breast carcinomas, a subgroup of highly proliferative tumors with poor outcome and no available targeted therapy. Functional studies indicate that silencing ATIP3 expression by siRNA increases breast cancer cell proliferation. Conversely, restoring endogenous levels of ATIP3 expression leads to reduced cancer cell proliferation, clonogenicity, anchorage-independent growth, and reduces the incidence and size of xenografts grown in vivo. We provide evidence that ATIP3 associates with the microtubule cytoskeleton and localizes at the centrosomes, mitotic spindle and intercellular bridge during cell division. Accordingly, live cell imaging indicates that ATIP3 expression alters the progression of cell division by promoting prolonged metaphase, thereby leading to a reduced number of cells ungergoing active mitosis.

Conclusions

Our results identify for the first time ATIP3 as a novel microtubule-associated protein whose expression is significantly reduced in highly proliferative breast carcinomas of poor clinical outcome. ATIP3 re-expression limits tumor cell proliferation in vitro and in vivo, suggesting that this protein may represent a novel useful biomarker and an interesting candidate for future targeted therapies of aggressive breast cancer.     

Generation of transgenic plants expressing plasma membrane-bound antibodies to the environmental pollutant microcystin-LR

In this paper we describe the engineering and regeneration of transgenic tobacco plants expressing a recombinant plasma membrane-retained antibody specific to microcystin-LR (MC-LR), the environmental toxin pollutant produced by cyanobacteria. The antibody was created by a genetic fusion of the antigen binding regions of the microcystin-specific single chain antibody, 3A8, with the constant regions from the murine IgG1κ, Guy’s 13, including a membrane retention sequence at the C-terminal end of the antibody heavy chain. The antibody produced in the leaves was shown to be functional by binding to MC-LR in an ELISA with antibody yields in transgenic plant leaves reaching a maximum of 1.2 μg g⁻¹ leaf f.wt (0.005% total soluble protein). Antibody-MC-LR complexes formed in leaves after addition of MC-LR to hydroponic medium around the roots of transgenic plant cultures.     

Sterol dependent regulation of human TM7SF2 gene expression: role of the encoded 3beta-hydroxysterol Delta14-reductase in human cholesterol biosynthesis

3Beta-hydroxysterol Delta(14)-reductase operates during the conversion of lanosterol to cholesterol in mammalian cells. Besides the endoplasmic reticulum 3beta-hydroxysterol Delta(14)-reductase (C14SR) encoded by TM7SF2 gene, the lamin B receptor (LBR) of the inner nuclear membrane possesses 3beta-hydroxysterol Delta(14)-reductase activity, based on its ability to complement C14SR-defective yeast strains. LBR was indicated as the primary 3beta-hydroxysterol Delta(14)-reductase in human cholesterol biosynthesis, since mutations in LBR gene were found in Greenberg skeletal dysplasia, characterized by accumulation of Delta(14)-unsaturated sterols. This study addresses the issue of C14SR and LBR role in cholesterol biosynthesis. Both human C14SR and LBR expressed in COS-1 cells exhibit 3beta-hydroxysterol Delta(14)-reductase activity in vitro. TM7SF2 mRNA and C14SR protein expression in HepG2 cells grown in delipidated serum (LPDS) plus lovastatin (sterol starvation) were 4- and 8-fold higher, respectively, than in LPDS plus 25-hydroxycholesterol (sterol feeding), resulting in 4-fold higher 3beta-hydroxysterol Delta(14)-reductase activity. No variations in LBR mRNA and protein levels were detected in the same conditions. The induction of TM7SF2 gene expression is turned-on by promoter activation in response to low cell sterol levels and is mediated by SREBP-2. The results suggest a primary role of C14SR in human cholesterol biosynthesis, whereas LBR role in the pathway remains unclear.     

Redox Control of Signal Transduction,Gene Expression and Cellular Senescence

Reactive oxygen species (ROS) act as subcellular messengers in such complex cellular processes as mitogenic signal transduction, gene expression, regulation of cell proliferation, replicative senescence, and apoptosis. They serve to maintain cellular homeostasis and their production is under strict control. However, the mechanisms whereby ROS act are still obscure. Here we review recent advances in our understanding of signaling mechanisms and recent data about the involvement of ROS in: (i) the regulation of the mitogenic transduction elements, particularly protein kinases and phosphatases; (ii) the regulation of gene expression; and (iii) the induction of replicative senescence and the role, if any, in aging and age-related disorders.     

Immunomarkers in gynecologic cytology: the search for the ideal 'biomolecular Papanicolaou test'

Harnessing the knowledge we have gained on the cell cycle disruption caused by human papillomaviruses (HPV) will likely lead to improved screening modalities for cervical cancer and its precursors. An easily applied biomarker that has high specificity and sensitivity would represent an attractive alternative or complement to cytology and HPV testing. To date, a number of promising markers have been investigated. These include p16(INK4A), MIB-1, BD-ProEx C, and L1. Newer possibilities involve a variety of gene products associated with aberrations of chromosome 3q, such as telomerase, p63, and PIK3CA, as well the combination of biomarkers such as p16(INK4A) and MIB-1 in the same assay. Although none of them has yet been incorporated into screening algorithms or found its way into routine practice, their performance characteristics remain a focus of current investigations. This review summarizes what we know and where we hope to go in translating basic pathobiology into clinical practice.